One of the many applications of a laser cutter on scale modeling is building brick walls. This post describes a proof of concept of building a piece of 1:87 (HO) brick wall on 5mm thick foam board using a Acmer S1 laser cutter...
One of the many applications of a laser cutter on scale modeling is building brick walls. This post describes a proof of concept of building a piece of 1:87 (HO) brick wall on 5mm thick foam board using a Acmer S1 laser cutter.
Engraving the foam board
The first step in the process is engraving a brick pattern on a 5mm thick black foam board. As the foam board is being engraved and not cut, its thickness is not relevant. However it's important to say that its color (black) determines the settings of the laser cutter, since cutting/engraving on a black surface requires less energy that, for instance, doing it on white foam board.
As the laser cutter works with vectorial paths, the first step is designing a vectorial pattern of a brick wall (how to do it is out of the scope of this document). For this specific task, a pattern of 8 rows of 3-4 bricks has been designed, each brick having a size of 3,6mm x 0,9mm with a gap of 0,1mm between bricks.
The svg file containing the above path is then loaded in LaserGRBL using two different settings:
A first engraving is done in a single pass with a speed of 1500 mm/min and a power of 1400mW (40% of power using a 3,5W laser).
A second engraving is done in a single pass with a speed of 1500 mm/min and a power of 1750mW (50% of power using a 3,5W laser). This engraving goes deeper than the previous one, creating a more irregular surface.
Filling the brick gaps
In order to paint the brick gaps, a primer (or a grey paint) is first applied. It can be applied with brush or airbrush, but always having into consideration to apply the less amount possible in order to avoid overfilling the gaps. In this specific case, Vallejo grey primer has been applied using a brush.
Painting the bricks
After filling the brick gaps, bricks are painted using a small piece of sponge lightly soaked in three different acrylic colors from Decoart Americana: brown, dark brown and red. Special care must be taken in not applying the sponge too charged of paint to avoid filling the brick gaps. After applying it randomly and, once dried, gently sanding with a piece of paper, the result obtained is that shown in the next photo.
Enhancing the contrast
The previous step gives a good mix of colors to the bricks, but makes them very similar by regions depending on how we applied the sponge. However, in a brick wall different brick colors can be found, mainly different due to the clay used to make them. In order to achieve that result, again Decoart Americana: brown and dark brown is applied to random bricks using a thin brush, getting a more realistic result.
Finally a matt varnish is applied randomly to make some brick glossier than other (any matt varnish is truly matt, they always add a given amount of gloss).
The final result
After all the above steps, the result in the first engraved brick set (that engraved at 1500min/mm, 1300mW power) is this:
And the result in the second engraved brick set (that engraved at 1500mm/min, 1750mW power) is this:
I find this last one very suitable for old walls, whereas the first one is suitable for most of the scenarios in which a normal brick wall is needed.
Note that the above photos are taken using a super macro setting. As previously said, each brick is 3,6mm width 0,9mm tall, and maybe the next photo gives a better idea of the resuls as should be seen in normal, non super macro, conditions (thanks Mike The Playmobil for holding the foam piece):
(*) The post heading image is included by courtesy of Darren Hester and is available on Flickr.
